The present invention relates to novel antigens, to methods for their production, to compositions containing them and to their use in the prevention, treatment and diagnosis of Lyme Disease in humans and other animals. In particular the present invention discloses novel serotypes/genotypes of the outer surface protein (Osp A) from the spirochete Borrelia burgdorferi, the causative agent of Lyme disease, and vaccine and diagnostic reagents based on B. burgdorferi of more than one subgroup.
Lyme disease in humans is a chronic progressive disease caused by B. burgdorferi, which is transmitted to humans mainly by Ixodes ticks. The disease attacks many organs, notably the skin, heart, liver, central and peripheral nervous system, kidneys as well as the musculoskeletal system.
Lyme disease itself is the most common vector borne infection in the USA and has been reported in every continent except Antarctica.
A number of groups have isolated and proposed the major surface protein (Osp A) of B. burgdorferi, as being a potential vaccine candidate for use against Lyme disease. For example, International patent application published under WO90/04411 (SIMBICOM) discloses the cloning and expression of an Osp A protein derived from B. burgdorferi B31 and its use as a vaccine, M. M. Simon and colleagues have cloned and expressed Osp A from B. burgdorferi ZS7 (European Patent Application No. 90117943.2 published under No. 0418 827), and demonstrated its protective capacity to induce antibodies in passively immunised SCID mice (PNAS: 87 1990, 3768-3772). Flavell and colleagues (Science (1991) 250 p553-556) have cloned and expressed the gene for Osp A from B. burgdorferi, N40 and have demonstrated its protective efficacy in C3H/He mice.
All isolates of B. burgdorferi identified above appear to be closely related. However we have now identified six subgroups of B. burgdorferi by analysing 55 spirochete isolates from different geographical areas and sources with series of immunological, biochemical and molecular genetic techniques. The finding of different subgroups of B. burgdorferi isolates have important implications for both effective vaccination and diagnosis of Lyme disease. Since ELISA diagnostic assays directed against a strain of which species N40 is a member would not or only partially cross react with species from other subgroups. Equally a vaccine based on only one Osp A for example from N40 would not provide optimal protection against B. bugdorferi from a different subgroup.
The present inventors have identified five additional subgroups of B. burgdorferi based on their Southern blotting and PCR amplification of Osp A sequences, and differences in the amino acid and nucleic acid sequences themselves and also in reactivity against monoclonal antibodies to Osp A proteins.
The surprising discovery that B. burgdorferi exhibits such heterogeneity has important implications for vaccines against, and diagnostics reagents for the detection of, Lyme disease, since vaccines or diagnostic based on an Osp A from one group of B. burgdorferi may not detect or protect against infection of B. burgdorferi from a second group. Indeed the present inventors have shown that whereas protection can be afforded by anti Osp A antibodies generated by recombinant Osp A or viable or killed organisms within a group of closely related strains, no or only partial, protection is observed if challenge is made with an organism from a different group.
A first subtype having representative ZS7, B31, N40 is referred to herein as group I (alternative nomenclature refers to group I strains as group A).
A second subgroup hereinafter group II (alternatively known as group B) is herein disclosed and is exemplified by the species ZQ1. This species has been deposited at the DSM Deutsche Sammlung von Mikroorganismen Und Zellkulturen of Mascheroderweg 91B D-3300 Braunschweig on Jul. 11, 1991 and given the accession No. DSM6606. This group is distinct in a number of ways from group I.
Firstly, plasmid analysis of strain ZQ1 when compared with representatives from group I shows that ZQ1 has at least two unique plasmids of 18 and 14 Kd. Furthermore plasmid of 16 Kb found in group I strains is absent from strain ZQ1. Secondly when examined by polyacrylamide gel electrophoresis Osp A from ZQ1 has an apparent molecular weight of 32 Kd.
Thirdly various monoclonal antibodies specific for Osp A of group I, such as the antibodies designated LA2 L26 LA28 LA33 do not react with Osp A from group II. LA2 and LA26 antibody are known and have been described in European patent application No. EP0418827. The hybridoma producing LA2 has been deposited under accession No. ECACC 89 09 1302 on Sep. 13, 1989 at the European Collection of animal cell cultures, Public health laboratory services Porton Down Wiltshire SP40J9. The hybridoma producing LA26 has been deposited at the same culture collection under accession No. 9005406 on Jun. 28, 1990.
However an other monoclonal antibody, LA31.1, does react with the Osp A species of subgroups I and II suggesting common epitopes among Osp A species of different subgroups do exist.
We have also characterised Osp A DNA from group II strains by PCR amplification. Two pairs of Osp A primers were used, these being designated prOsp A1-prOsp A4 and prOsp A1-prOsp A2.
The primers have the following sequences:
prOsp A1: 5xe2x80x2-GGGAATAGGT CTAATATTAG CC-3xe2x80x2xe2x80x83xe2x80x83(SEQ.ID NO:13)
prOsp A2: 5xe2x80x2-TGCCTGAATT CCAAGCTGCA-3xe2x80x2xe2x80x83xe2x80x83(SEQ. ID NO:14)
prOsp A4: 5xe2x80x2-GCAGTTAAAG TTCCTTCAAG AACATAGC-3xe2x80x2xe2x80x83xe2x80x83(SEQ. ID NO:15)
and correspond to nucleotides at positions 138-160 (prOsp A1), 611-638 (prOsp A4), and 759-778 (prOsp A2), of ZS7 Osp A respectively. Total DNA of Group II, B. burgdorferi are distinguishable from that of Group I in that group II will not permit successful PCR (polymerase chain reaction) amplification when prOsp A1 and prOsp A2 are used as primers whereas total DNA from group I will permit a successful reaction. In contrast, when prOsp A1 and prOsp A4 are used as primers, then both DNA""s of group I and group II will undergo polymerase chain reaction.
These results show that group II, B. burgdorferi have a different Osp A sequences to group I Osp As.
Equally, group II Osp A DNA, can be distinguished from group I Osp A DNA by Southern blotting utilising Osp A ZS7 sequence as a probe. Digesting genomic DNA of B. burgdorferi group II with the restriction enzyme Hind III shows a different banding pattern than that of group I strain.
For example a group I strain reveals two hybridisation fragments of 1.2 kb and 0.3 kb whereas a group II strain expressed two fragments of 0.9 kb and 0.4 kb.
Also, passive immunisation of SCID mice with immune sera to Osp A from group II will not protect against B. burgdorferi group I challenge.
Finally when compared to the sequence of Osp A ZS7 the DNA and amino acid sequence of ZQ1 strain Osp A Sequence ID 1 and 2 (i.e. a group II strain), demonstrates the substantial variation between a group I and group II strain at both the DNA and amino acid levels.
The surprising inability to protect against heterologous challenge means that a vaccines based on a single Osp A from a group I organism may be ineffective against infection with B. burgdorferi from group II organism and vice versa. Consequently there is a need for a vaccine which will protect against group II infection.
Accordingly there is provided DNA sequence encoding an Osp A derived from a B. burgdorferi characterised in that polymerase chain reaction amplification will take place utilising prOsp A1-A4 primers, but not prOsp A1-A2, and the invention further provides purified or isolated Osp A encoded thereby.
Preferably the Osp A of the present invention will not react with monoclonal antibody LA2 or LA26. Most preferably the Osp A of the present invention will have a relative molecular weight of 32 kDa as determined by SDS electrophoresis utilising molecular weight markers as standard.
Preferably the Osp A is derived from either ZQ1 or NE11H or other group II strain.
Preferably the protein is at least 70% pure as determined by SDS polyacrylamide gel electrophoresis, in particular at least 80% pure, and most preferably at least 95% pure. Preferably the Osp A antigen has a relative molecular weight of 32 kDa as determined by SDS polyacrylamide gel electrophoresis. Preferably the Osp A antigen will not react with the monoclonal antibody LA2.
In another aspect of the present invention there is provided a DNA sequence substantially identical to the DNA sequence encoding Osp A from ZQ1. By substantially identical it is meant a DNA sequence contains a sequence which is at least 85% identical and preferably 90% identical to the ZQ1 Osp A sequence depicted in Sequence ID 1. The mature protein starts at position 17 and preferably the invention provides a DNA sequence which is at least 95% identical to the sequence encoding the mature protein as indicated in Sequence ID 2.
In an alternative embodiment there is provided an Osp A containing an amino acid sequence substantially identical to the sequence set forth in sequence ID 2. The term substantially identical in relation to the amino acid sequence means amino acid sequence which is at least 85% and preferably 90% identical to the protein sequence depicted in figure and preferably at least 85% identical to the mature protein.
The present inventors have also found utilising the same biochemical and immunological techniques other groups of B. burgdorferi unrelated to other group I or II. Two isolates characteristic of group III (or group C) are the strain designated as 19857 and 21038. Such strains, like group II, strains react under PCR conditions with prOsp A1-A2 but not with prOsp A1-A4. However they differ from group II strains when analysed by Southern blotting when utilising a ZS7 probe and restriction enzyme HindIII. Such analysis reveal hybridisation fragments of 4.0 kb and 0.5 kb. In addition they react with monoclonal antibody LA26, but not LA2.
We have now sequenced utilising PCR technology, and expressed a DNA sequence encoding an Osp A from strain 19857. The DNA and amino acid sequence are depicted in sequence ID No. 3 and 4. A comparison with sequence from other/groups shows that the Osp A only has approximately 65% identity at the DNA/and amino acid levels with Osp A from other subgroups.
Accordingly the present invention provides a DNA sequence encoding an Osp A protein wherein the DNA sequence is substantially identical to the DNA sequence of Sequence ID 3. In a further embodiment there is provided an Osp A protein which has an amino acid sequence substantially identical to the protein as disclosed in Sequence ID 4.
The term substantial identical as used herein with respect to the sequences depicted in sequence ED No.3 and 4 mean at least 70% identity, preferably 80-85% identity more preferably 85-95% identical.
A fourth subgroup, group IV (or group D) of B. burgdorferi, as exemplified by a Swedish isolate ACA-1 differs from any of groups I, II or III, M.
Jonsson et al.(Int. Conf. Lyme Borreliosis 1990). This group will not undergo PCR with either prOsp A1-A2 or prOsp A1-A4. Their Osp A""s react with monoclonal antibody LA26 but not with LA2.
Southern blotting analysis when utilising a ZS7 probe and restriction enzyme HindIII reveal a single hybridisation fragment of about 1.7 kb.
Isolated or recombinant Osp A from group IV also form part of the present invention as do vaccine or diagnostic compositions containing them.
By utilising the same Biochemical techniques, the present inventors have identified representatives from group V and group VI. A group V isolates is known as 20047 and a representative of group VI is the strain known as S90.
Isolated Osp A from group V and VI strain also form part of the invention.
The present invention also relates to immunogenic derivatives of the OspA from group II, group III, group IV and group V or group VI B. burgdorferi. 
The term immunogenic derivative as used herein encompasses any molecule such as a truncated or hybrid protein which are immunologically reactive with antibodies generated by infection of a mammalian host with a group II, or group III or group IV, or group V or group VI, B. burgdorferi and which preferably do not react with the monoclonal antibodies designated LA2. Such derivatives may be prepared by substitution, or rearrangement of aminoacids or by chemical modifications thereof.
Immunogenic fragments of the protein, which may be useful in the preparation of subunit vaccines, may be prepared by expression of the appropriate gene fragments or by peptide synthesis, for example using the Merrifield synthesis (The Peptides, Vol 2., Academic Press, NY, page 3).
The immunogenic derivative of the invention can be a hybrid, that is, a fusion polypeptide containing additional sequences which can carry one or more epitopes for other B. burgdorferi immunogens including Osp A and/or Osp B, or other immunogens from, for example other pathogens. Alternatively, the immunogenic derivative of the invention can be fused to a carrier polypeptide such Hepatitis B surface or core antigen or to another carrier which has immunostimulating properties, as in the case of an adjuvant, or which otherwise enhances the immune response to the Osp A protein or derivative thereof, or which is in expressing, purifying or formulating the protein or derivative thereof.
The invention also extends to the Osp A protein or immunogenic derivative thereof when chemically conjugated to a macromolecule using a unconventional linking agent such as glutaraldehyde (Geerlings et al, (1988) J. Immunol. Methods,106, 239-244).
Particularly preferred derivatives are hybrid fusion proteins of the influenza non-structural protein NS1 and Osp A or truncated Osp A derivatives. These can advantageously be produced by recombinant DNA techniques in high yields in E. coli. 
Accordingly the present invention provides an Osp A protein fused to the N terminal portion of the protein NS1 from Influenza. Preferably the Osp A portion of the fusion protein is truncated so as to remove at least the hydrophobic signal sequence. More preferably the N terminal 16 amino acids representing the signal sequence and the cysteine residue which is the first amino-acid of the mature protein of the Osp A are missing.
Preferably the NS1 part of the fusion protein comprises from 3 to 81 amino acids of the N-terminal portion of the gene. The longer the NS1 part of the fusion is preferred, since this permits higher expression levels of proteins.
These hybrid proteins of the present invention are recoverable from the soluble fraction as non aggregated protein, in contrast to the native recombinant Osp A and are expressed at a higher level. The proteins retain their ability to react with monoclonal antibodies raised against native Osp A and are capable of raising a protective immune response in laboratory animals e.g. mice and rabbits.
In an embodiment of the invention there is provided an NS1 Osp A fusion protein from the Osp A group, known as group I, e.g. an Osp A from strain ZS7 as disclosed in EP 0418-827, or B31 as described by Howe et al. Science 227 p645, 1985, or N40 as described by Flavell et al. Such Osp A""s show significant sequence homology at both the DNA and amino acid levels and are cross protective.
In a further embodiment of the present invention there is provided an NS1-Osp A wherein the Osp A is from the group known as group II. For example the Osp from B. burgdorferi strain ZQ1 as described herein.
In a yet further embodiment of the present invention there is provided an NS1-Osp A wherein the Osp A is from the group known as group III. For example strain 19857. The invention further provides a group IV NS1-Osp A, for example wherein the Osp A is derived from the strain AcaI.
The present invention further provides a DNA sequence which encodes an NS1-Osp A fusion protein as described herein. In particular the present invention provides a DNA sequence encoding an NS1-Osp A protein and the protein itself as shown in Sequence ID Nos 5 to 12 attached herewith.
The proteins of the present invention can be produced by methods standard in the art for producing other Osp A proteins from known strains. For example, the Osp A proteins maybe produced in E. Coli utilising recombinant DNA technology. In particular, the proteins may be produced as full length immature proteins or mature proteins. The proteins may also be expressed as fusion proteins, such as NS1-fusion proteins.
A DNA sequence encoding the proteins of the present invention (e.g. Osp A ZQ1 or Osp A 19857) can be synthesized using standard DNA synthesis techniques, such as by enzymatic ligation as described by D. M. Roberts et al in Biochemistry 1985, 24, 5090-5098, by chemical synthesis, by in vitro enzymatic polymerization, or by PCR technology utilising for example a heat stable polymerase, or by a combination of these techniques.
Enzymatic polymerisation of DNA may be carried out in vitro using a DNA polymerase such as DNA polymerase I (Klenow fragment) in an appropriate buffer containing the nucleoside triphosphates dATP, dCTP, dGTP and dTTP as required at a temperature of 10xc2x0-37xc2x0 C., generally in a volume of 50 xcexcl or less. Enzymatic ligation of DNA fragments may be carried out using a DNA ligase such as T4 DNA ligase in an appropriate buffer, such as 0.05M Tris (pH 7.4), 0.01M MgCl2, 0.01M dithiothreitol, 1 mM spermidine, 1 mM ATP and 0.1 mg/ml bovine serum albumin, at a temperature of 4xc2x0 C. to ambient, generally in a volume of 50 ml or less. The chemical synthesis of the DNA polymer or fragments may be carried out by conventional phosphotriester, phosphite or phosphoramidite chemistry, using solid phase techniques such as those described in xe2x80x98Chemical and Enzymatic Synthesis of Gene Fragmentsxe2x80x94A Laboratory Manualxe2x80x99 (ed. H. G. Gassen and A. Lang), Verlag Chemie, Weinheim (1982), or in other scientific publications, for example M. J. Gait, H. W. D. Matthes, M. Singh, B. S. Sproat, and R. C. Titmas, Nucleic Acids Research, 1982, 10, 6243; B. S. Sproat and W. Bannwarth, Tetrahedron Letters, 1983, 24, 5771; M. D. Matteucci and M. H Caruthers, Tetrahedron Letters, 1980, 21, 719; M. D. Matteucci and M. H. Caruthers, Journal of the American Chemical Society, 1981, 103, 3185; S. P. Adams et al., Journal of the American Chemical Society,1983, 105, 661; N. D. Sinha, J. Biernat, J. McMannus, and H. Koester, Nucleic Acids Research, 1984, 12, 4539; and H. W. D. Matthes et al., EMBO Journal, 1984, 3, 801.
Alternatively, the coding sequence can be derived from B. burgdorferi mRNA, using known techniques (e.g. reverse transcription of mRNA to generate a complementary cDNA strand), and commercially available cDNA kits.
DNA polymers which encode mutants of the Osp A proteins may be prepared by site-directed mutagenesis of the cDNA which codes for the protein by conventional methods such as those described by G. Winter et al in Nature 1982, 299, 756-758 or by Zoller and Smith 1982; Nucl. Acids Res., 10, 6487-6500, or deletion mutagenesis such as described by Chan and Smith in Nucl. Acids Res., 1984, 12, 2407-2419 or by G. Winter et al in Biochem. Soc. Trans., 1984, 12, 224-225.
The process of the invention may be performed by conventional recombinant techniques such as described in Maniatis et. al., Molecular Cloningxe2x80x94A Laboratory Manual; Cold Spring Harbor, 1982-1989.
In particular, the process may comprise the steps of:
i) preparing a replicable or integrating expression vector capable, in a host cell, of expressing a DNA polymer comprising a nucleotide sequence that encodes the protein or an immunogenic derivative thereof;
ii) transforming a host cell with said vector,
iii) culturing said transformed host cell under conditions permitting expression of said DNA polymer to produce said protein; and
iv) recovering said protein.
The term xe2x80x98transformingxe2x80x99 is used herein to mean the introduction of foreign DNA into a host cell. This can be achieved for example by transformation, transfection or infection with an appropriate plasmid or viral vector using e.g. conventional techniques as described in Genetic Engineering; Eds. S. M. Kingsman and A. J. Kingsman; Blackwell Scientific Publications; Oxford, England, 1988. The term xe2x80x98transformedxe2x80x99 or xe2x80x98transformantxe2x80x99 will hereafter apply to the resulting host cell containing and expressing the foreign gene of interest.
The expression vectors are novel and also form part of the invention.
The replicable expression vectors may be prepared in accordance with the invention, by cleaving a vector compatible with the host cell to provide a linear DNA segment having an intact replicon, and combining said linear segment with one or more DNA molecules which, together with said linear segment encode the desired product, such as the DNA polymer encoding the Osp A protein, or derivative thereof, such as an NS1 Osp A-fusion protein under ligating conditions.
Thus, the DNA polymer may be preformed or formed during the construction of the vector, as desired.
The choice of vector will be determined in part by the host cell, which may be prokaryotic or eukaryotic. Suitable vectors include plasmids, bacteriophages, cosmids and recombinant viruses.
The preparation of the replicable expression vector may be carried out conventionally with appropriate enzymes for restriction, polymerisation and ligation of the DNA, by procedures described in, for example, Maniatis et al cited above.
The recombinant host cell is prepared, in accordance with the invention, by transforming a host cell with a replicable expression vector of the invention under transforming conditions. Suitable transforming conditions are conventional and are described in, for example, Maniatis et al cited above, or xe2x80x9cDNA Cloningxe2x80x9d Vol. II, D. M. Glover ed., IRL Press Ltd, 1985.
The choice of transforming conditions is determined by the host cell. Thus, a bacterial host such as E. coli may be treated with a solution of CaCl2 (Cohen et al, Proc. Nat. Acad. Sci., 1973, 69, 2110) or with a solution comprising a mixture of RbCl, MnCl2, potassium acetate and glycerol, and then with 3-[N-morpholino]-propane-sulphonic acid, RbCl and glycerol. Mammalian cells in culture may be transformed by calcium co-precipitation of the vector DNA onto the cells. The invention also extends to a host cell transformed with a replicable expression vector of the invention.
Culturing the transformed host cell under conditions permitting expression of the DNA polymer is carried out conventionally, as described in, for example, Maniatis et al and xe2x80x9cDNA Cloningxe2x80x9d cited above. Thus, preferably the cell is supplied with nutrient and cultured at a temperature below 50xc2x0 C.
The product is recovered by conventional methods according to the host cell. Thus, where the host cell is bacterial, such as E. coli it may be lysed physically, chemically or enzymatically and the protein product isolated from the resulting lysate. Where the host cell is mammalian, the product may generally be isolated from the nutrient medium or from cell free extracts. Conventional protein isolation techniques include selective precipitation, adsorption chromatography, and affinity chromatography including a monoclonal antibody affinity column.
The proteins of the present invention when expressed in E. Coli as full length proteins produce lipoprotein micelles which are immunogenic. Such full length lipoproteins form part of the present invention.
It will be appreciated that all the proteins of the present invention may find utility in vaccine and diagnostic applications.
Furthermore, it will be appreciated that other antigenic components such as other Osp A antigens or Osp B from B. burgorferi isolates or antigens from other pathogens may be included in a vaccine composition of the present invention. Additionally other antigens from other organisms may be present in the vaccine.
The Osp A antigens utilised in the compositions of the present invention include immunogenic fragments of Osp A, i.e. fragments of Osp A containing immunogenic B or T-cell epitopes, or fusion proteins containing such epitopes, including fusions of Osp A""s from different groups.
In an aspect of the present invention there is provided a vaccine or diagnostic composition comprising an Osp A or derivative thereof from a subgroup II strain. In particular one characterised in that it is encoded by a DNA sequence which will permit successful polymerase chain reaction to take place utilising prOsp A1-A4 primers, but not prOsp A1-A2, the protein being in admixture with suitable excipient or carrier. More particularly there is provided a composition comprising an Osp A or derivative thereof from a group II strain having an amino acid sequence substantially identical to the protein sequence depicted in sequence ID No.2.
Such compositions may advantageously also contain an Osp A derivative from a subgroup I strain.
Accordingly the present provides in a preferred embodiment a composition, preferably a vaccine composition comprising an Osp A antigen derived from a subgroup I B. burgdorferi, and an Osp A antigen from a subgroup II, B. burgdorferi. 
Preferably the Osp A antigen from group I are selected from group, B31, ZS7 and N40.
Preferably the Osp A antigen from group II is selected from the group ZQ1, NE11H.
The present invention also provides a vaccine or diagnostic composition comprising an OspA or derivative from a subgroup III strain, the protein being a admixture with a suitable excipient or carrier. More particularly the vaccine or diagnostic composition comprises an OspA or derivative thereof having an amino acid sequence substantially identical to the protein sequence depicted in sequence ID No.4.
Preferably the OspA is derived from strain 19857.
The invention also provides a vaccine or diagnostic composition comprising an Osp A or derivative from subgroup IV, V or VI.
In a preferred embodiment there is provided a combination vaccine comprising at least two OspA""s or derivatives thereof from different B. burgdorferi subgroups. Such vaccine compositions provide protection from a wider range of Borrelia infections than hitherto. Preferably the vaccine comprises an Osp A from each of groups I to IV and most preferably an Osp A from each of group I to VI.
In the vaccine of the invention, an aqueous solution of the protein(s) can be used directly. Alternatively, the protein, with or without prior lyophilization, can be mixed or absorbed with any of the various known adjuvants. Such adjuvants include, but are not limited to, aluminium hydroxide, muramyl dipeptide and saponins such as Quil A. Particularly preferred adjuvants are, MPL (monophosphoryl lipid A) and 3D-MPL (3Deacylated monophosphoryl lipid A). A further preferred adjuvant is known as QS21. 3 DMPL can be obtained by the methods disclosed in UK patent No. 2220211, whereas QS21 can be obtained by the method disclosed in U.S. Pat. No. 5,057,540. As a further exemplary alternative, the proteins can be encapsulated within microparticles such as liposomes or associated with oil in water emulsions. In yet another exemplary alternative, the proteins can be conjugated to an immuostimulating macromolecule, such as killed Bordetella or a tetanus toxoid.
The proteins of the present invention may be expressed by live vectors such as BCG, Listeria or Salmonella and formulated as live vaccines using such vectors.
Vaccine preparation is generally described in New Trends and Developments in Vaccines, Voller et al. (eds.), University Park Press, Baltimore, Md., 1978. Encapsulation within liposomes is described by Fullerton, U.S. Pat. No. 4,235,877. Conjugation of proteins to macromolecules is disclosed, for example, by Likhite, U.S. Pat. No. 4,372,945 and Armor et al., U.S. Pat. No. 4,474,757.
Use of Quil A is disclosed by Dalsgaard et al., Acta Vet Scand, 18:349 (1977). Use of 3D-MPL is described by Ribi et al. Microbiology (1986) LEVIE et al. (Eds) American Soc. for Microbiol. Wash. D.C. pp 9-13.
The amount of the protein of the present invention present in each vaccine dose is selected as an amount which induces an immunoprotective response without significant, adverse side effects in typical vaccines. Such amount will vary depending upon which specific immunogen is employed and whether or not the vaccine is adjuvanted. Generally, it is expected that each dose will comprise 1-1000 xcexcg of protein, preferably 1-200 xcexcg. An optimal amount for a particular vaccine can be ascertained by standard studies involving observation of antibody titres and other responses in subjects. Following an initial vaccination, subjects may receive an additional administration to enhance their immune response.